Monolithic column chromatography

ABSTRACT

Provided herein are methods of liquid column chromatography in which preparative chromatography is performed in-line with analytical chromatography. In particular aspects a monolithic preparative column is used to purify an analyte of interest from a mixture of other substances by applying the mixture to the column, reversing the flow through the column to elute the analyte, which is applied to an analytical column provided in-line with the preparative column. In other aspects, a single monolithic column is used to perform both the preparative chromatography and analytical chromatography steps in succession. In another aspect, a chromatography system is provided to perform preparative and analytical chromatography using a single monolithic column.

FIELD OF THE INVENTION

The present invention relates generally to the field of liquid columnchromatography.

BACKGROUND OF THE INVENTION

Analytical liquid chromatography (e.g., high performance liquidchromatography or HPLC) is commonly used in the detection andquantitation of low molecular weight substances in biological samplesand body fluid samples (e.g., blood, serum, or plasma). Such samplescontain proteins and proteinaceous molecules, which can accumulate onmany types of HPLC columns, thereby causing irreversible damage to suchcolumns. For this reason, it is desirable to remove the proteins andother large molecular weight species prior to analysis of the sample forthe analyte of interest. Methods of removal of proteins includeprecipitation, membrane filtration, and liquid-liquid or liquid-solidphase extraction.

An alternate method of removing proteins from a sample is preparativeliquid chromatography. In order to adapt such a method to highthroughput assays, high flow rates, short elution times, and moderateoperating pressures are desirable. Accordingly, porous support materialsfor use in column chromatography which, simultaneously offer a selectiveretention of low molecular weight analytes (molecular weight<5000Dalton), and make possible quantitative separation of proteins and othermacromolecular components in a directly injected sample have recentlybeen developed. One example of a column comprising such a porous supportis a new column for use in HPLC, known as a monolithic column.Monolithic columns, in contrast to traditional HPLC columns thatcomprise packed particles, contain a single, solid compound as thestationary phase. This stationary phase is usually made up of a networkof polymethacrylate or polystyrene copolymers, or bonded silica formingpores of varying size. Thus, in monolithic columns the mobile phase mustflow through the pores of the solid stationary phase. Molecules withinthe mobile phase are then retained to a greater or lesser extent withinthe pores of the stationary phase (small molecules diffuse into thepores and are retained while large molecules are excluded from the poresand are not retained). Retention of small molecules may be furtherenhanced by binding to specific compounds incorporated into the interiorof the pores.

SUMMARY OF THE INVENTION

Provided herein are methods of performing preparative liquidchromatography, using a monolithic column, in-line with analyticalliquid chromatography. In such methods, an analyte or analytes ofinterest are separated from other substances in a complex mixture usinga monolithic column under conditions whereby the analyte is retained onthe column. The analyte is then eluted and supplied to an in-lineanalytical column for further separation and detection. Such methodsoffer the advantage of utilizing a monolithic column in the preparativechromatography, which allows for higher flow rates at moderate operatingpressures, resulting in quick separations. The further combining ofpreparative chromatography in-line with analytical chromatographydecreases the amount of handling by the operator which results in afast, efficient, and inexpensive method amenable to high-throughputassays.

In one aspect of the invention, there are provided chromatographicmethods for detecting one or more analytes in a sample containing amixture of other substances. Such methods comprise: a) separating theone or more analytes from the other substances in a mixture using afirst chromatography column comprising a monolithic sorbent havingmacropores and mesopores, using a first mobile phase under conditionssuch that the one or more analytes are retained on the first column andother substances are removed, b) eluting the one or more retainedanalytes by applying a second mobile phase to the column, c) directingthe eluted one or more analytes to a second chromatography columnin-line with the first column for further separation, and d) detectingthe one or more analytes following the separation in step c).

In some embodiments the second mobile phase is applied to the column inthe same direction as the flow in step a). In other embodiments, thesecond mobile phase is applied to the column in the opposite directionof the flow in step a).

In some embodiments, a monolithic column is used to separate smallmolecular weight analytes of interest from a mixture of large molecularweight species. Thus, a sample is loaded onto a monolithic column,comprising macropores and mesopores under conditions such that smallmolecule analytes are retained, while larger molecules are excluded andwashed from the column with the eluent. After the large molecular weightspecies have been removed, the small molecule analyte is eluted from thecolumn with a reverse flow of mobile phase and supplied directly to anin-line analytical column for further separation and analysis.

The above method can be applied to obtain preparative samples of smallmolecular weight analyte from various types of body fluids and usingmonolithic columns with various physical characteristics.

In another aspect of the invention, there are provided methods forachieving multiple chromatographic separations of one or more analytesfrom other substances in a sample using a single column. Such methodscomprise: a) achieving a first chromatographic separation of one or moreanalytes from other substances, the separation occurring by applying thesample to a chromatography column comprising a monolithic sorbent havingmacropores and mesopores, using a first mobile phase under conditionssuch that the one or more analytes in the sample are retained on thecolumn and other substances are removed, b) eluting the one or moreretained analytes by applying a second mobile phase to the column in theopposite direction of the flow in step a), c) applying the eluted one ormore analytes to the column under conditions whereby a secondchromatographic separation is achieved. Such methods allow for the useof fewer columns and fewer HPLC pumps, resulting in a reduction in costas well as savings in space. In addition, use of the column foranalytical separation allows for enhanced recovery of analyte that mayhave remained adsorbed to the column during the first chromatographicseparation.

In some embodiments of the above aspect of the invention, the firstchromatographic separation is a preparative chromatographic separationand the second chromatographic separation is an analytical separation.In this method, a mixture containing small molecule analytes and largermolecules is applied to the monolithic column under conditions such thatthe small molecule analytes are retained on the column, whereas thelarge molecules pass through the column. One or more analytes ofinterest are then eluted using a reverse flow of a small volume of anorganic solvent and recovered into a precolumn reservoir. The eluted oneor more analytes are then resupplied to the monolithic column, and thesystem run under conditions sufficient for chromatographic separationand detection of the analyte or analytes of interest.

In certain embodiments of the above aspect of the invention, step c)further comprises retaining the one or more analytes on the column andeluting the one or more analytes using reverse flow. The eluted analytesmay then be reapplied to the column under conditions whereby a thirdchromatographic separation is achieved.

In other embodiments of the above aspect of the invention, step c)further comprises running the one or more analytes through the columnand monitoring the effluent for the one or more analytes. Monitoring maybe performed by any of a number of instruments or detectors well-knownto those of skill in the art. For example, analytes may be detectedusing mass spectrometrometers, UV/V is absorbance detectors,photodiodearray detectors, fluorescence detectors, refractive indexdetectors, conductivity detectors, and the like.

In still other embodiments of the above aspect of the invention, step c)further comprises collecting the one or more analytes into fractionsfollowing the second (or third, etc.) chromatographic separation. Suchfractions may be subjected to further analysis by chromatographicmethods or other standard analytical methods.

The above methods can be applied to obtain preparative samples of smallmolecular weight analyte from various types of body fluids and usingmonolithic columns with various physical characteristics.

In another aspect of the invention, there is provided a chromatographysystem for achieving multiple chromatographic separations of one or moreanalytes from other substances in a sample using a single monolithiccolumn. Such a system comprises as a central feature a multiport valveand a column comprising a continuous monolithic sorbent havinginterconnected macropores and mesopores. The system further includes amobile phase supply, a sample injector, a reservoir, a detector, and awaste line. The system is configured as follows: the mobile phase supplyconnected to the sample injector, which is connected to one port of themultiport valve having individual ports. Each port of the multiportvalve is further connected to one of the following: a reservoir (havinga first end and a second end and wherein the reservoir is adapted tohold eluted analyte) wherein the first end of the reservoir is in fluidcommunication with a port of the valve and the second end of thereservoir is in fluid communication with a first opening of a column; asecond opening of the column; a detector; and a waste line. Themultiport valve is switchable between a first position and a secondposition. In the first position of the valve, the mobile phase supply(via the sample injector) is connected to the valve which is connectedto the sample loop which is connected to the first opening of thecolumn. The second opening of the column is connected to the valve whichis further connected to the detector. In the second position of thevalve, the orientation of the column with respect to the system isreversed so that the mobile phase supply is connected, via the valve tothe second opening of the column. The first opening of the column isconnected to the sample loop which is connected to the valve which isconnected to the waste line.

The two operating positions of the multiport valve determine thedirection of flow of mobile phase through the column. In the firstposition, fluid from the mobile phase supply travels via the sampleinjector to the valve which directs the flow through the reservoir, andinto the first end of the column. Flow exits the column via the secondopening of the column and enters the valve and is directed to adetector. When the valve is in the second position, the mobile phaseenters the column through the second opening of the column and exits viathe second opening, thus providing a flow of mobile phase through thecolumn in the opposite direction as the flow of mobile phase when thevalve is in the first position. Exiting mobile phase is further directedto a waste line.

In a particular embodiment of the above aspect of the invention, thesystem further comprises a second multiport valve. In this system thetwo valves are connected in tandem. Each port of the first multiportvalve is connected to one of the following: a sample injector; areservoir, having a first end and a second end and wherein the reservoiris adapted to hold eluted analyte, wherein the first end is in fluidcommunication with a port of the first multiport valve and the secondend is in fluid communication with a first opening of a column, a secondopening of the column; and a second multiport valve. The secondmultiport valve is further connected to one or more detectors and awaste line. The first multiport valve is switchable between a firstposition and a second position so that the valve controls the directionof the flow of mobile phase through the column. The second multiportvalve is switchable between a first position and a second position sothat the valve controls the flow of effluent to the detector or thewaste line. Thus, the user of the system can change the orientation ofthe column with respect to the system (i.e., reverse the flow of solventthrough the column) using the first valve. Further, the user candetermine whether a particular detector or a waste line is in-line usingthe second valve.

In such a system, a sample is applied to the column using the solventdelivery system and the sample injector under conditions whereby smallmolecules are retained on the column while large molecular weightspecies flow through the column and are not retained. The solvent andlarge molecular weight species may be conducted to a waste line or to anin-line detector to monitor removal of the large molecules. Once thelarge molecular weight species have been washed from the column, flow ofsolvent through the column is reversed and the analyte is eluted fromthe column into the reservoir. Flow is reversed again and the analyte isreapplied to the column for further analytical separation. Following theanalytical separation, the eluted analyte may be conducted to any of theone or more in-line detectors.

“Monolithic column” as used herein comprises a material (e.g., silica,glass, glass-ceramic, or polymeric components) having interconnectedcontinuous macropores with a median diameter larger than 0.1 μm. Amonolithic column also may additionally contain mesopores in the wallsof the macropores. Mesopores preferably have a median diameter between 2and 100 nm.

The interconnected macropores in the porous materials of a monolithiccolumn may exhibit median diameters ranging from 0.1 to 50 μm; apreferred range for the median diameters of the macropores is from 0.2to 20 μm or 0.2 to 10 μm.

Mesopores present in the walls of the macropores exhibit mediandiameters ranging from 2 to 100 nm; a preferred range for the mediandiameters of the mesopores is from 2 to 50 nm, and especially a rangefrom 5 to 30 nm being preferred.

“Phenyl,” “C-2,” “C-8,” and “C-18” as used herein refer to functionalgroups present on a column packing material. For example, a phenylcolumn exposes the material flowing through the column to unsubstitutedphenyl groups, while a C-18 column exposes the material flowing throughthe column to unsubstituted straight or branched chain 18-carbon alkylgroups.

In some embodiments, the inner surface of the macro or mesopore ischemically modified. In particular aspects, the interior of themesopores of a monolithic column are coated with a C4, C8, C18, orphenyl material to assist in the retention of hydrophobic analytes.

“Liquid chromatography” (LC) as used herein means a process of selectiveretention or retardation of one or more components of a fluid solutionas the fluid flows through a column containing stationary material(s)made of a finely divided substance and/or a material having capillarypassageways. Retention results from the relative partitioning of thecomponents of the mixture between the stationery phase and the bulkfluid phase (i.e., mobile phase), the later of which moves through thestationery materials. LC is used for analysis and separation of mixturesof two or more substances. LC includes, for example, high turbulenceliquid chromatography (HTLC), preparative chromatography, and analyticalchromatography (e.g., HPLC).

“High turbulence liquid chromatography” (HTLC) as used herein refers tothe use of turbulent flow to enhance the rate of mass transfer duringcolumn chromatography, improving the separation characteristicsprovided. This is in contrast to traditional HPLC analysis which relieson column packings in which laminar flow of the sample through thecolumn is the basis for separation of the analyte of interest from thetest sample. HTLC has been applied for sample preparation to detectdrugs prior to analysis by mass spectrometry. See, e.g., Zimmer et al.,J. Chromatogr. A 854: 23-35 (1999); see also, U.S. Pat. Nos. 5,968,367;5,919,368; 5,795,469; and 5,772,874.

“Preparative chromatography” as used herein refers to coarse separationof a particular analyte from a mixture containing other substances thatare grossly different from the analyte (e.g., a small molecule analytemay be separated from a mixture containing proteins and other largemolecular weight species). Such methods involve the selective retentionof a particular solute or analyte in a complex mixture by a column,while other components are not retained. The analyte is then selectivelyremoved from the column and may be collected for further use oranalysis. Typically, preparative chromatographic separations arefollowed by a finer separation, which allows for the separation ofclosely related molecules (i.e., analytical chromatography). Preparativechromatography does not necessarily involve large samples, or largecolumns (although very large columns are often used in preparativechromatography). In preparative chromatography, column diameters canrange from a few millimeters to a meter or more, and mobile phasevolumes may range from a few milliliters to hundreds of liters. Inpreparative chromatography, analytes eluted from the column may becollected in an in-line reservoir (e.g., sample loop or tubing).Alternatively, analytes, following elution from the preparative column,may be directed to an in-line analytical column for further analysis.

“Analytical chromatography” as used herein refers to a fine separationof closely related molecules (e.g., molecules of similar molecularweights). In analytical chromatography, analytes separated on a column,eluted from the column, and monitored or detected. The term “analyticalcolumn” as used herein refers to a chromatography column havingsufficient chromatographic plates to effect a separation of an analytefrom other materials in a sample, wherein such a separation issufficient to allow detection and determination of the presence oramount of the analyte.

In methods provided herein a single monolithic column is used for bothpreparative chromatography and analytical chromatography. This isaccomplished by changing the conditions under which each separation isperformed. Such conditions include flow rate, composition of the mobilephase, and the direction of flow of mobile phase through the column.

“Separating” as used herein, refers to the process characterized by thespatial separation of the components of a mixture based on theirpartitioning differential between phases (i.e., mobile and stationaryphases) in relative motion. Separating results from loading the sampleonto the column and washing the column following loading.

“Loading” as used herein, refers to the application of a sample to thecolumn until the entire sample is contained within the column.

“Washing” as used herein, refers to the process of flowing solventthrough the column after loading so as to remove substances not adsorbedon the column or substances from which the analyte is to be separated.Multiple washes are possible using different wash solutions.

“Sample” as used herein, refers to any solution comprising a mixture oflarge and small molecular weight species. Such samples include any typeof biological samples such as body fluids or samples derived from cellculture, microorganisms, plants, or animals.

“Body fluid” as used herein means any fluid that can be isolated fromthe body of an individual. For example, “body fluid” may include blood,plasma, serum, bile, saliva, urine, tears, perspiration, synovial fluid,peritoneal fluid, bronchial-alveolar lavage, CSF, and the like.

“Small molecular weight species” or a “small molecule analyte” as usedherein refers to a molecule that typically has a molecular weight ofless than 5,000 daltons, more typically less than 1,000 daltons, andmost typically less than 500 daltons. Following preparative isolationfrom the monolithic column, the analytes are then subjected toanalytical chromatographic separation and detection.

“Large molecular weight species” as used herein refers to a moleculehaving a molecular weight in the range of one thousand to many millionsof daltons. Examples include proteins, proteinaceous substances, nucleicacids, polysaccharides, and other polymers. “Proteinaceous substances”as used herein refer to any material that includes a polypeptide as partof the molecule. Proeteinaceous materials include glycoproteins,proteoglycans, lipoproteins, and the like. The term protein includes theterms “polypeptide,” and “peptide,” which refer to a polymer of aminoacid residues. The term applies to amino acid polymers in which one ormore amino acid residue is a synthetic chemical analogue (e.g.,para-methyl-tyrosine, para-chloro-phenylanine, and the like) of acorresponding naturally occurring amino acid, as well as to naturallyoccurring amino acid polymers. Amino acids can be in the L or D form solong as the binding function of the peptide is maintained. Peptides canbe of variable length, generally between about 4 and 200 amino acids.Peptides may be cyclic, having an intramolecular bond between twonon-adjacent amino acids within the peptide, e.g., backbone to backbone,side-chain to backbone and side-chain to side-chain cyclization.

“In-line” as used herein refers to steps performed in sequence and in anautomated fashion and without the need for operator intervention. Forexample, by careful selection of valves and connector plumbing, two ormore chromatography columns can be connected as needed such thatmaterial is passed from one column to the next without the need for anymanual handling steps. Alternatively, one column may be used inconjunction with one or more valves and connector plumbing so that thedirection of the flow of mobile phase through the column may bereversed, allowing for an eluted analyte to be reapplied to the column.Such systems may require electronic programming of controlling software.In preferred embodiments, the selection of valves and plumbing iscontrolled by a computer pre-programmed to perform the necessary steps.In some embodiments, the chromatography system is connected in-line to adetector system, e.g., a mass spectrometry system.

“Off-line,” in contrast, as used herein refers to a procedure requiringmanual intervention of an operator. Thus, if samples are subjected toprecipitation, and the supernatants are then manually loaded into anautosampler, the precipitation and loading steps are off-line from thesubsequent steps.

“Eluent” as used herein refers generally to the liquid or gas entering achromatographic bed (e.g., a column) used to effect a separation by“elution.”

“Effluent” refers generally to a liquid that flows out of something. Asused herein, “effluent” refers to the solvent flowing out of a column.Effluent may contain substances not retained on the columna or analyteseluted from the column.

“Reservoir” refers generally to a vessel or container entity for holdinga liquid. As used herein “reservoir” may be used to hold the analyteafter elution from the column. The analyte may be held in the reservoiruntil it is, for example, reloaded onto the column from which it waseluted, or directed to another column. Examples of reservoirs as usedherein include a sample loop or tubing.

“Mobile phase source” as used herein refers to a vessel that holdsmobile phase prior to its being utilized in a chromatographicseparation.

“Hydrophobic” as used herein means not dissolving in water.“Hydrophobic” compounds include long straight or branched chain alkanes.A hydrophobic solvent is a solvent that is capable of dissolving ahydrophobic compound.

The choice of solvents or mobile phase used depend on the nature of thecolumn used in a particular preparative or analytical separation. Forexample, solvents typically used with reversed phase columns typicallyinclude any miscible combination of water and various organic liquids(the most common are methanol or acetonitrile).

In certain embodiments, an analyte may be purified by applying a sampleto a column under conditions where the analyte of interest is reversiblyretained by the column, while one or more other materials are notretained. In these embodiments, a first mobile phase condition can beemployed where the analyte of interest is retained by the column, and asecond mobile phase condition can subsequently be employed to removeretained material from the column, once the non-retained materials arewashed through. The second mobile phase may be phased in gradually togenerate a concentration gradient, usually under computer controldirecting the composition of mobile phase over time, or by an immediatechange in the mobile phase. In some embodiments, removal is accomplishedwith the use of a small volume of an organic solvent. The retainedmaterials may also be removed from the column by “backflushing” thecolumn, or reversing the direction of flow of the mobile phase. Suchbackflushing may be performed with the same mobile phase used inapplying the analyte to the column or may be a different mobile phasefor removing the retained material. This may be particularly convenientfor material that is retained at the top of the column. Alternatively,an analyte may be purified by applying a sample to a column under mobilephase conditions where the analyte of interest elutes at a differentialrate in comparison to one or more other materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-B. Schematic of a two-column chromatography system comprising amonolithic preparative column and an analytical column. FIG. 1A showsthe system in the first position. FIG. 1B shows the system in the secondposition.

FIGS. 2A-B. Schematic of a single column chromatography systemcomprising a single monolithic column and one multiport valve, assembledso that the monolithic column may be used for both preparative andanalytical chromatography. FIG. 2A shows the valve in the first positionand the direction of the solvent flow during column equilibration,sample loading, and detection of the eluted analyte. FIG. 2B shows thevalve in the second position during the isolation of the retainedanalyte following the preparative chromatography.

FIGS. 3A-C. Schematic of a single column chromatography systemcomprising a single monolithic column and two multiport valves (4) and(7) assembled so that the monolithic column may be used for bothpreparative and analytical chromatography. FIG. 3A shows the first andsecond multiport valves both in the first position during columnequilibration and sample loading. FIG. 3B shows the position of thefirst and second multiport valves (second position and first position,respectively) during the elution of analytes. FIG. 3C shows the positionof the first and second multiport valves (first position and secondposition, respectively) during the elution and detection of the analyte.

FIG. 4A-C. Schematic of the HTLC system used in the analysis ofestradiol in a sample of serum using a single monolithic column forextraction and analysis, as described in Example 2.

FIG. 5. Chromatograms showing the separation of estradiol andD8-estradiol internal standard in a serum sample from the large moleculebackground, produced with the use of a monolithic column for preparativechromatography in-line with analytical HPLC.

FIG. 6. Chromatograms showing the separation of estradiol andD8-estradiol internal standard in a serum sample from the large moleculebackground, produced with the use of a monolithic column for bothpreparative chromatography and analytical chromatography.

FIG. 7A-C Schematic of the HTLC system used in the analysis of estradiolin a sample of serum using a monolithic column for preparativechromatography followed by in-line analytical chromatography using asecond column, as described in Example 1.

DETAILED DESCRIPTION OF THE INVENTION

In particular aspects, a preparative monolithic column is suppliedin-line with an analytical column in a chromatography system. Such asystem is set forth in FIG. 1A-B. Thus, referring to FIG. 1A, a firstmobile phase source (1) is connected to a solvent delivery system (2)which is connected to a sample injector (3) which is connected to oneport of a multiport valve (4). Other ports of the multiport valve (4)are connected to the top end of the preparative monolithic column (5),the bottom end of the preparative monolithic column (5), waste (6), thetop end of the analytical column (9), and a second solvent deliverysystem (8), which is further connected to a second mobile phase source(7). The bottom end of the analytical column is further connected to adetector (10), which is connected to an optional data integrator (11).

In the operation of the above system, mobile phase (1) is supplied tothe system with a solvent delivery system (2). Samples are injected intothe system downstream of the solvent delivery system with a sampleinjector (3) with the multiport valve (4) in the first position (FIG.1A). The sample is transferred with mobile phase or buffer (1) using thesolvent delivery system (2) onto the preparative column (5) containing amonolithic sorbent. The analytes of interest are selectively retained onthe column (5) based on the size of the analyte, while the remainingbiological materials (proteins etc.) are passed to the waste (6). Afterthe multiport valve (4) has been switched to the second position (FIG.1B), the analyte is eluted with the aid of an organic solvent (7)supplied by a second solvent delivery system (8), running in the reversedirection through preparative column (5) and supplied to the downstreamanalytical column (9). The analytical separation takes place underconditions sufficient to separate the analytes of interest. The elutedanalytes are measured in the detector (10), and the data are evaluatedin the integrator (11). The multiport valve is then switched to thefirst position so that the preparative column can be conditioned bymeans of the solvent delivery system (2) for a new preparative cycle.

In other aspects, a single monolithic column is used in both preparativeand analytical separations. There are at least two configurations ofsuch a system. One example of such a system is set forth in FIG. 2A-B.Thus, referring to FIG. 2A, a mobile phase reservoir (1) is connected toa solvent delivery system (2) which is connected to a sample injector(3) which is connected to one port of a multiport valve (4). Other portsof the multiport valve (4) are connected to a reservoir (i.e., a sampleloop) (5), the second opening of the column (6), a detector (7), andwaste (8), which is connected to an optional data integrator (notshown). The sample loop connects to the first opening of the column (6).

During operation of the above system, mobile phase (1) is supplied tothe system using a solvent delivery system (2). Sample is injected intothe system with a sample injector (3), passed through the multiportvalve (4) set in the first position, through the sample loop (5) andonto the monolithic column (6) under conditions such that the analyte ofinterest is retained on the column while large molecular weight speciesare swept off of the column and through the detector (see FIG. 2A). Thevalve (4) is then switched to the second position (see FIG. 2B),reversing the flow of mobile phase through the column, and the analyteis eluted from the column and into the sample loop (5). The valve (4) isswitched back to the first position (see FIG. 2A) and the analyte isre-supplied to the column (6). The analyte may then be eluted off thecolumn under conditions sufficient to separate the analyte or analytesof interest from each other or from other substances retained on thecolumn and detected using the detector (7).

In a preferred embodiment of the above aspect of the invention, thesystem further comprises a second multiport valve, preferably connectedin tandem with the first multiport valve. Such a system is set forth inFIG. 3A-C. Thus, referring to FIG. 3A, a first mobile phase source (1)is connected to a solvent delivery system (2), which is connected to asample injector (3), which is connected to one port (shown as port #6)of a first multiport valve (4). Other ports of the multiport valve (4)are connected to a reservoir (i.e., sample loop) (5), the bottom end ofthe column (6), and a second multiport valve (7). The second valve (7)is further connected to waste (8) and a detector (9). The detector maybe further connected to an optional data integrator (not shown).

During the operation of the above system, mobile phase (1) is suppliedto the system using solvent delivery system (2). Sample is injected intothe system with a sample injector (3), passed through the first valve(4) set in first position through the sample loop (5) and onto themonolithic column (6) under conditions such that the analyte of interestis retained on the column while large molecular weight species are sweptoff of the column, through second valve (7) in the first position andinto waste (8) (as shown in FIG. 3A). The first valve (4) is switched tothe second position (as shown in FIG. 3B) and the analyte is eluted fromthe column and into the sample loop (5). The first valve (4) is thenswitched back to the first position (as shown in FIG. 3C) and theanalyte is resupplied to the column (6). The second valve (7) isswitched to the second position (as shown in FIG. 3C) so that flow ofeffluent will pass through the detector (9) (see FIG. 3C). The analyteis eluted off the column under conditions sufficient to separate theanalyte or analytes of interest from each other or from other substancesretained on the column.

Mobile Phase Supply

A mobile phase supply comprises a mobile phase source and a solventdelivery system. Such a solvent delivery system is a pumping device suchas commercially available HPLC pumps, which provide solvent or mobilephase to a column. Such pumps generally provide pulse-free flows, flowrates ranging from 0.1-10 mL/min, accurate control of flow rate,generation of high pressure (up to 6000 psi), and corrosion- andsolvent-resistant components. Reciprocating pumps consist of a smallchamber into which the solvent is pumped by the back and forth motion ofa motor-driven piston. Two check valves, which open and closealternately, control the direction and flow of solvent in and out of acylinder. Single-piston pumps use specially designed cams to permit veryrapid refill times, producing a more continuous flow. The disadvantageof pulsed flows with reciprocating pumps is often overcome by using apulse damper. The use of a dual-piston pump, which operates with thepistons moving out of phase with each other, offers a reasonablesolution for pulse-free fluid delivery.

A mobile phase “gradient” or “gradient elution” as used herein refers tosteady changes in the mobile phase composition during a chromatographicrun. The main purpose of gradient elution is to elute analytes that arestrongly retained by the column faster, while having the weakly retainedanalytes eluted more slowly so that eluted analytes produce wellresolved peaks upon detection. For example, in reversed phasechromatography, starting with a low content of the organic solvent inthe eluent allows the weakly retained analytes to be separated. Stronglyretained analytes will remain on the adsorbent surface at the top of thecolumn, or will move very slowly. Increasing the amount of organiccomponent in the eluent (e.g., acetonitrile) allows strongly retainedcomponents to move faster, because of the steady increase of thecompetition for the adsorption sites by the organic solvent.

Mobile phase gradients may be generated through high pressure mixing,which requires a pump for each solvent, or low pressure mixing whichrequires only one pump. In high-pressure mixing systems, individual highpressure pumps are used to provide each solvent. The outlet of each pumpis either connected to a mixing connector (usually referred to as a “T”since there are normally two inlet lines and one outlet line) or to amixing chamber. Thus, the two solvents are blended en route to theinjector and column, that is, mixing is accomplished on thehigh-pressure side of the pumps. The generation of a mobile phasegradient created from three solvents may be accomplished by utilizingthree separate pumps. In low-pressure systems, mixing is accomplishedprior to the pump, at its low-pressure side and the overall flow rate iscontrolled by a single pump. Proportioning valves, normally solenoidoperated, are used to deliver the individual solvents. The controllersimply divides the signal according to the percentage of each componentand each valve is opened for the proper period of time. Usually thevalves deliver the individual solvents into a mixing chamber which thenfeeds the blended solvent to the pump. In some systems, the valves feedthe mobile phase components through a mixing connector directly to thehigh-pressure pump. Programmable flow rate control is desirable forgradient generation by either method.

Sample Injector

A manual sample injector that is typically used comprises a 2-positionvalve that includes a fixed sample loop (e.g., 20 or 100 μl). In oneconfiguration, the valve is set so that the flow from the pump is sentdirectly into the column; when the position of the valve is switched,the flow from the pump is diverted through the sample loop and into thecolumn, thus supplying the sample to the column. Valves withelectrically or pneumatically actuated position switches arecommercially available and may be used.

Automated sample injectors (i.e., autosamplers) may be used in inventionmethods and systems. Such autosamplers can store and sequentially injectmultiple samples are useful in high-throughput screening methods.Autosamplers are commercially available from a variety of sources.

Multiport Valve

Multiport valves or reversing valves are available in manyconfigurations from many commercial sources. Such valves may have, forexample, six, or, eight, or ten, or more ports and up to six positions.Such valves may be optionally controlled with an actuator, allowing forautomated control of the position of the valve.

In one example, the multiport valve has 6 ports and two operatingpositions. Thus, the valve may be connected simultaneously to aninjector (with a solvent delivery system connected upstream), the topend of a column, the bottom end of a column and a detector. Thecomponents may be configured so that the multiport valve, which has twooperating positions, controls the direction of the flow of solventthrough the column. In the first position, solvent flows from thesolvent delivery system, through the sample injector, into the valve,through the sample loop and into the top of the column. The solvent thenflows through the column, out of the bottom of the column and to thedetector or waste line. In the second position, solvent flows throughthe solvent delivery system, into the valve, and into the bottom of thecolumn. The solvent then flows in the opposite direction through thecolumn, out of the top of the column and to the detector or waste line.

In another example, a second valve may be connected in tandem with thefirst valve. In this system, a solvent delivery system is connected to asample injector which is connected one port of a multiport valve. Theother ports of the multiport valve are connected to the top end of thecolumn (via a sample loop) and the bottom end of the column, and to thesecond multiport valve. The second multiport valve is further connectedto one or more detectors, or a detector and a waste line. The secondvalve, therefore, controls the flow of effluent from the column toeither of one or more in-line detectors or waste. Thus, when the firstvalve is in the first position, the injector is connected to the valvewhich is connected to the sample loop which is connected to the top endof the column. The bottom end of the column is connected to the valvewhich is further connected to the second valve. The second valve has twooperating positions so that when the second valve is in one position,the first valve is connected (via the second valve) to a detector or,when the valve is in the second position, to a waste line. An optionalsecond detector may replace the waste line. In another example, a secondchromatography column is connected to the second valve. In this system,the first valve is connected (via the second valve) to the second column(and to an optional downstream detector) or, when the valve is in thesecond position, to a waste line.

Columns

A monolithic column comprises a “monolith,” a continuous bed consistingof a single piece of a highly porous solid material (see e.g., TennikovaT B, Svec F (1993) J Chromatogr 646:279). A distinguishing feature ofthis medium is that the mobile phase is forced to flow through the largepores of the medium. As a consequence, mass transport is enhanced byconvection and has a positive effect on the separation. Monolithicsupports commercially available include: silica gel based monolithicbeds, polyacrylamide based monolithic beds, and rigid organic gel basedmonolithic beds.

Silica gel-based monolithic beds are solid rods of silica monolith thathave been prepared according to a sol-gel process. This process is basedon the hydrolysis and polycondensation of alkoxysilanes in the presenceof water-soluble polymers. The method leads to “rods” made of a singlepiece of porous silica with a defined bimodal pore structure havingmacropores (of about 2 μm) and mesopores (of about 0.013 μm) whensmaller rods intended for analytical purposes are prepared. Thesecolumns have about 80% porosity, which is 15% more than columns packedwith standard particulate packing (see e.g., Nakanishi K, Soga N (1991)J Am Ceram Soc 74:2518; Cabrera K, Wieland G, Lubda D, Nakanishi K, SogaN, Minakuchi H, Unger K K (1998) Trends Anal Chem 17:50).

Polyacrylamide-based monolithic beds are made of swollen polyacrylamidegel compressed in the shape of columns. Such columns rely on thepolymerization of monomers and in the chromatographic column. In thepresence of salt, the polymer chains form aggregates into large bundlesby hydrophobic interaction, creating voids between the bundles(irregularly shaped channels) large enough to permit a high hydrodynamicflow. Following polymerization, the bed is compressed by connecting itto an HPLC pump adjusted to a flow rate equal or higher than that usedin subsequent runs. The resulting bed can be regarded as a rod or plugpermeated by channels through which the eluent can pass upon applicationof pressure. The polymer chains form a dense, homogeneous network ofnodules consisting of microparticles with an average diameter of 2 μm.The channels between the nodules are large enough to permit a highhydrodynamic flow (see e.g., Hjerten S, Liao J-L, Zhang R (1989) JChromatogr 473:273; Liao J-L, Zhang R, Hjerten S (1991) J Chromatogr586:21).

Rigid organic gel-based monolithic beds are prepared by free radicalpolymerization of a mixture of a polymerizable monomer, optionally withfunctional groups, such as glycidyl methacrylate, ethylenedimethacrylate, a crosslinking agent, a radical chain initiator, such as2,2′-azobisisobutyronitrile, and porogenic solvents (cyclohexanol anddodecanol) in barrels of an appropriate mold in the case of glycidylmethacrylate-co-ethylene dimethacrylate (GMA-EDMA) monoliths (see e.g.,Svec F, Tennikova T B (1991) J Bioact Compat Polym 6:393; Svec F,Jelinkova M, Votavova E (1991) Angew Macromol Chem 188:167; Svec F,Frechet J M J (1992) Anal Chem 64:820). Another method uses free radicalpolymerization of a mixture of styrene and divinylbenzene (as across-linking reagent) using 2,2′-azobisisobutyronitrile as an initiatorand porogenic solvents (dodecanol and toluene) (Merhar M, J LiqChromatogr 24:2429 (2001)). After polymerization, the formed block ofpolymer is washed, e.g. with methanol, followed by a methanol-watermixture (50:50) and distilled water to remove porogenes and residualmonomers from the polymer. After this, the monolithic bed is ready forderivatization to achieve a desired chemistry or immobilization ofligands. GMA-EDMA monoliths have active epoxide groups which can easilybe further modified using various chemicals, e.g. diethyl amine, propanesulfone for ion exchange chromatography, e.g. butyl groups forhydrophobic interaction chromatography and any desired protein ligandfor affinity chromatography. Alternatively, the epoxide groupscontaining monolith material can be modified to obtain polar groups onthe surface, e.g. by using acids, e.g. sulfuric acid; to obtain themonolith material in hydrolized form that carries OH groups. Dependingon the adsorption and elution conditions, a monolith carrying polargroups, e.g. hydroxyl (OH) groups or amino (NH₂) groups, is suitable forbeing used in a variety of adsorption principles, e.g. the so-called“normal phase” chromatography (Dorsey J G, Foley J P, Cooper W T,Barford R A, Barth H G (1990) Anal. Chem. 62:324 R) or the so-called“hydrophilic interaction” chromatography (Alpert A J (1990) J.Chromatogr. 499:17), the so-called “cohydration/cosovent exclusionpromoted chromatography” (Validated Biosystems: Purification Tools forMonoclonal Antibodies, Cagnon P (1996), 103) or the so-called “hydrogenbond chromatography” (Fujita T, Suzuki Y, Yamauti J, Takagahara I, FujiiK., Yamashita J, Horio T (1980) J. Biochem. (Tokyo), 87 (1):89).

A number of different columns are commercially available for use inanalytical chromatography. These columns differ in the column packingmaterial and thus, the means by which analytes are retained and includereversed-phase or hydrophobic interaction, ion exchange, size exclusionor gel permeation, and affinity columns. Numerous column packings areavailable for analytical chromatographic separation of samples, andselection of an appropriate separation protocol is an empirical processthat depends on the sample characteristics, the analyte of interest, theinterfering substances present and their characteristics, etc. For HPLC,polar, ion exchange (both cation and anion), hydrophobic interaction,phenyl, C-2, C-8, and C-18 columns are commercially available. Duringchromatography, the separation of materials is effected by variablessuch as choice of eluant (also known as a “mobile phase”), choice ofgradient elution and the gradient conditions, temperature, etc.

In reversed phase (RP) liquid chromatography, the typical polarstationary phase is replaced with a hydrophobic stationary phase, thusthe phase is “reversed.” A reversed-phase column, then, retainshydrophobic analytes, which are eluted more readily as the proportion ofthe hydrophobic component of the mobile phase is increased. Exemplarycolumns include phenyl, C-2, C-4, C-8, and C-18.

Affinity chromatography is based on selective non-covalent interactionbetween an analyte and specific molecules. It is very specific, but notvery robust. It is often used in biochemistry in the purification ofproteins protein constructs (e.g., fusion proteins, tagged proteins, andthe like).

Detection and Identification of Analyte

In some embodiments, a mass spectrometer is used in-line for detectionand identification of the analyte.

The terms “mass spectrometry” or “MS” as used herein refer to methods offiltering, detecting, and measuring ions based on their mass-to-chargeratio, or “m/z.” In general, one or more molecules of interest areionized, and the ions are subsequently introduced into a massspectrographic instrument where, due to a combination of magnetic andelectric fields, the ions follow a path in space that is dependent uponmass (“m”) and charge (“z”). See, e.g., U.S. Pat. No. 6,204,500,entitled “Mass Spectrometry From Surfaces;” U.S. Pat. No. 6,107,623,entitled “Methods and Apparatus for Tandem Mass Spectrometry;” U.S. Pat.No. 6,268,144, entitled “DNA Diagnostics Based On Mass Spectrometry;”U.S. Pat. No. 6,124,137, entitled “Surface-Enhanced PhotolabileAttachment And Release For Desorption And Detection Of Analytes;” Wrightet al., Prostate Cancer and Prostatic Diseases 2:264-76 (1999); andMerchant and Weinberger, Electrophoresis 21:1164-67 (2000), each ofwhich is hereby incorporated by reference in its entirety, including alltables, figures, and claims.

For example, in a “quadrupole” or “quadrupole ion trap” instrument, ionsin an oscillating radio frequency field experience a force proportionalto the DC potential applied between electrodes, the amplitude of the RFsignal, and m/z. The voltage and amplitude can be selected so that onlyions having a particular m/z travel the length of the quadrupole, whileall other ions are deflected. Thus, quadrupole instruments can act asboth a “mass filter” and as a “mass detector” for the ions injected intothe instrument.

Moreover, one can often enhance the resolution of the MS technique byemploying “tandem mass spectrometry,” or “MS/MS.” In this technique, afirst, or parent, ion generated from a molecule of interest can befiltered in an MS instrument, and these parent ions subsequentlyfragmented to yield one or more second, or daughter, ions that are thenanalyzed in a second MS procedure. By careful selection of parent ions,only ions produced by certain analytes are passed to the fragmentationchamber, where collision with atoms of an inert gas to produce thesedaughter ions. Because both the parent and daughter ions are produced ina reproducible fashion under a given set of ionization/fragmentationconditions, the MS/MS technique can provide an extremely powerfulanalytical tool. For example, the combination offiltration/fragmentation can be used to eliminate interferingsubstances, and can be particularly useful in complex samples, such asbiological samples.

Additionally, recent advances in technology, such as matrix-assistedlaser desorption ionization coupled with time-of-flight analyzers(“MALDI-TOF”) permit the analysis of analytes at femtomole levels invery short ion pulses. Mass spectrometers that combine time-of-flightanalyzers with tandem MS are also well known to the artisan.Additionally, multiple mass spectrometry steps can be combined inmethods known as “MS/MS^(n).” Various other combinations may beemployed, such as MS/MS/TOF, MALDI/MS/MS/TOF, or SELDI/MS/MS/TOF massspectrometry.

Ions can be produced using a variety of methods including, but notlimited to, electron ionization, chemical ionization, fast atombombardment, field desorption, and matrix-assisted laser desorptionionization (“MALDI”), surface enhanced laser desorption ionization(“SELDI”), photon ionization, electrospray ionization, and inductivelycoupled plasma.

The term “electron ionization” as used herein refers to methods in whichan analyte of interest in a gaseous or vapor phase is interacted with aflow of electrons. Impact of the electrons with the analyte producesanalyte ions, which may then be subjected to a mass spectroscopytechnique.

The term “chemical ionization” as used herein refers to methods in whicha reagent gas (e.g. ammonia) is subjected to electron impact, andanalyte ions are formed by the interaction of reagent gas ions andanalyte molecules.

The term “fast atom bombardment” as used herein refers to methods inwhich a beam of high energy atoms (often Xe or Ar) impacts anon-volatile test sample, desorbing and ionizing molecules contained inthe sample. Samples are dissolved in a viscous liquid matrix, such asglycerol, thioglycerol, m-nitrobenzyl alcohol, 18-crown-6 crown ether,2-nitrophenyloctyl ether, sulfolane, diethanolamine, andtriethanolamine. The choice of an appropriate matrix for a compound orsample is an empirical process.

The term “field desorption” as used herein refers to methods in which anon-volatile test sample is placed on an ionization surface, and anintense electric field is used to generate analyte ions.

The term “matrix-assisted laser desorption ionization,” or “MALDI” asused herein refers to methods in which a non-volatile sample is exposedto laser irradiation, which desorbs and ionizes analytes in the sampleby various ionization pathways, including photo-onization, protonation,deprotonation, and cluster decay. For MALDI, the sample is mixed with anenergy-absorbing matrix, which facilitates desorption of analytemolecules.

The term “surface enhanced laser desorption ionization,” or “SELDI” asused herein refers to another method in which a non-volatile sample isexposd to laser irradiation, which desorbs and ionizes analytes in thesample by various ionization pathways, including photo-ionization,protonation, deprotonation, and cluster decay. For SELDI, the sample istypically bound to a surface that preferentially retains one or moreanalytes of interest. As in MALDI, this process may also employ anenergy-absorbing material to facilitate ionization.

The term “electrospray ionization” or ESI as used herein refers tomethods in which a solution is passed along a short length of capillarytube, to the end of which is applied a high positive or negativeelectric potential. Solution reaching the end of the tube, is vaporized(nebulized) into a Jet or spray of very small droplets of solution insolvent vapor. This mist of droplets flows through an evaporationchamber which is heated slightly to prevent condensation and toevaporate solvent. As the droplets get smaller the electrical surfacecharge density increases until such time that the natural repulsionbetween like charges causes ions as well as neutral molecules to bereleased.

The term “Atmospheric Pressure Chemical Ionization,” or “APCI,” as usedherein refers to methods that are similar to ESI; however, APCI producesions by ion-molecule reactions that occur within aplasma at atmosphericpressure. The plasma is maintained by an electric discharge between thespray capillary and a counter electrode. Then ions are typicallyextracted into the mass analyzer by use of a set of differentiallypumped skimmer stages. A counterflow of dry and preheated N2 gas may beused to improve removal of solvent. The gas-phase ionization in APCI canbe more effective than ESI for analyzing less-polar species.

The term “inductively coupled plasma” as used herein refers to methodsin which a sample is interacted with a partially ionized gas at asufficiently high temperature to atomize and ionize most elements.

The term “ionization” as used herein refers to the process of generatingan analyte ion having a net electrical charge equal to one or moreelectron units. Negative ions are those ions having a net negativecharge of one or more electron units, while positive ions are those ionshaving a net positive charge of one or more electron units.

The term “operating in negative ion mode” refers to those massspectrometry methods where negative ions are detected. Similarly,“operating in positive ion mode” refers to those mass spectrometrymethods where positive ions are detected.

The term “desorption” as used herein refers to the removal of an analytefrom a surface and/or the entry of an analyte into a gaseous phase.

In those embodiments, such as MS/MS, where parent ions are isolated forfurther fragmentation, collision-induced dissociation, or “CID,” isoften used to generate the ion fragments for further detection. In CID,parent ions gain energy through collisions with an inert gas, andsubsequently fragment by a process referred to as “unimoleculardecomposition.” Sufficient energy must be deposited in the parent ion sothat certain bonds within the ion can be broken due to increasedvibrational energy.

In other embodiments, any of a variety of standard HPLC detectors can beused for the detection of the analyte upon elution from the analyticalcolumn. In this case, the elution of a compound from the column isdetected as a peak in a chromatogram. The retention time of the peak isused to identify the compound, and the peak height (or area) isproportional to the amount of the compound in the sample. The “retentiontime” is the time required for an analyte to pass through achromatographic system and is measured from the time of injection to thetime of detection. Ideally, each analyte of interest will have acharacteristic retention time. However, the retention of an analyteoften differs considerably between experiments and laboratories due tovariations of the eluent, the stationary phase, temperature, and thesetup of the chromatographic system. Therefore the retention time of thetest analyte is compared to that of one or more standard compounds underidentical conditions. An appropriate detector exhibits good sensitivity,good stability, reproducibility, linear response over a few orders ofmagnitude, short response time, and ease of operation. Such detectorsinclude, but are not limited to, UV/V is absorbance detectors,photodiodearray detectors, fluorescence detectors, refractive indexdetectors, and conductivity detectors.

UV/V is absorbance detectors consisting of a scanning spectrophotometerwith grating optics can be used. The independent or combined use of aDeuterium source (UV range, 190-360 nm) with a Tungsten source (visiblerange, 360-800 nm) provides a simple means of detecting absorbingspecies as they emerge from the column.

Photodiode-array (PDA)-based instruments are UV/Vis absorbance detectorsthat permit very rapid collection of data over a selected spectralrange. Absorbance spectral data for each chromatographic peak can becollected and stored. Stored data may be compared with the spectrum of apure standard from a library. The PDA detector is useful in theidentification of components that are difficult to resolve (overlappingpeaks) since the characteristic spectrum for each of the unresolvedcomponents is likely to be different.

Fluorescence detectors are useful in the detection of analytes thatexhibit a chemiluminescent property such as fluorescence orphosphorescence. They are more sensitive than UV absorbance detectors byat least one order of magnitude. Fluorescence is typically observed bydetection of the grating-isolated emission radiation at a 90-degreeangle to the excitation beam. The number of fluorescing species can beenhanced by a post-column derivatization (PCD) reaction of the elutedcompounds (or pre-column derivatization reaction of the sample itself)with special reagents.

Refractive index (RI) detectors respond to nearly all solutes. Thedifference in the refractive index of the reference mobile phase versusthe column effluent results in the detection of separated components aspeaks on the chromatogram. Because of its extreme sensitivity to themobile phase, this detector may not be used without adequatepulse-damping within the LC pump, nor is it suitable for gradientapplications because of the changing mobile phase composition. Thedetection limits are usually lower than those observed with absorbancedetectors.

Conductivity detectors provide high-sensitivity detection of all chargedspecies. This detector may be used with an HPLC system for the simpleand reliable quantification of anions, cations, metals, organic acids,and surfactants down to the ppb level. The addition of a chemicalsuppressor between the column and conductivity detector serves to reducethe eluant conductivity, allowing the use of gradient elution and thedetermination of ppb levels with minimum baseline drift. For a typicaldetermination of low levels of anions, the eluant is converted to itsweakly ionized low-conductivity acid (e.g., Na2CO3 to carbonic acid),reducing the background noise. At the same time, the analyte anions areconverted to their corresponding high-conductivity acids (e.g., NaCl toHCl), increasing the relative analyte signal.

Data Collection

A record of the detector response may be obtained using a chart recorderor an integrator. Automated data and method storage, data processing,and reporting can be performed with standard PC-based data collectionpackages.

Example 1

A sample of serum was assayed for estradiol using a monolithic columnfor preparative chromatography followed by in-line analyticalchromatography using a second column.

An HTLC system was used which comprised two LC pumps (quaternary pump orbinary), two multiport valves, a monolithic C18 column (50×4.6 mm,mesopore 130 Å, macropore 2 μm, porosity >80%), an ether-linked phenylphase column (100×2.0 mm, 80 Å, 4 μm), a 100 μL sample loop, and a massspectrometer (“ms”). The system was configured as shown in FIG. 7A-C.

The first pump was connected to port 2 of the first multiport valve, the100 μL sample loop was connected to ports 3 and 4, and the first column(the monolithic C18 column) was located between ports 1 and 5. Thesecond multiport valve was connected, via port 3, to the first multiportvalve at port 6. The second valve was further connected to the secondcolumn (the ether-linked phenyl phase column), which was furtherconnected to a mass spectrometer (“MS”) via port 4, and a waste line viaport 2.

The solvents used were as follows:

-   -   Solvent A: 0.1% formic acid    -   Solvent B: 100% methanol

The samples were processed by adding 200 μL of serum and diluting with300 μL of 20% formic acid in water and adding 25 μL of the internalstandard in methanol. The columns were equilibrated with both multiportvalves in the “LOAD” position (see FIG. 7A) using 100% solvent A fromthe first pump. 80 μL of the processed sample was injected onto thecolumn using 100% solvent A at a flow rate of 4-5 mL/min for 30 seconds.The first multiport valve was switched to the “ELUTE” position (see FIG.7B) and the column was backflushed with 100% solvent B from the firstpump at a flow rate of 1 mL/min for 60 seconds to elute retainedanalytes from the column into the 200 μL sample loop. The secondmultiport valve was switched to the “ELUTE” position (see FIG. 7C) andthe eluted analytes were applied to the second column using 95% solventA:5% solvent B from the first pump at a flow rate of 1 mL/min for 15seconds. The second multiport valve was switched to the “LOAD” position(see FIG. 7B) and the analytes were eluted with a gradient of 95%solvent A: 5% solvent B to 100% solvent B generated by the second pumpand run at a flow rate of 1.6 mL/min over 200 seconds. Eluted analyteswere detected using the in-line mass spectrometer. A peak correspondingto a retention time of 2.48 minutes was observed and determined to beestradiol. D8-estradiol, run as an internal standard, exhibited aretention time of 2.48 minutes. The resulting chromatograms are shown inFIG. 6.

To recharge the column for subsequent samples, the first column wasbackflushed with 100% solvent B from the first pump at a flow rate of4-5 mL/min for 60 seconds with the first multiport valve in the “ELUTE”position and the second multiport valve in the “LOAD” position (see FIG.7B). The first multiport valve was switched to the “LOAD” position (seeFIG. 7A) and the column was equilibrated with 100% solvent A from thefirst pump at a flow rate of 5 mL/min for 40 seconds.

Example 2

A sample of serum was assayed for estradiol using a single monolithiccolumn for both preparative chromatography and analyticalchromatography.

An HTLC system was used which comprised a quaternary pump, two multiportvalves, a monolithic C18 column (50×4.6 mm, mesopore 130 Å, macropore 2μm, porosity >80%), a 100 L sample loop, a 200 μL sample loop, and amass spectrometer. The system was connected as in FIG. 4A-C. Thequaternary pump (not shown) was connected to port 2 of the firstmultiport valve, the 100 μL sample loop was connected to ports 3 and 4,and the 200 μL sample loop was connected between port 5 and the column.The second multiport valve was connected, via port 3, to the firstmultiport valve at port 6. The second valve was further connected to amass spectrometer (“MS”) via port 4 and a waste line via port 2.

The solvents used were as follows:

-   -   Solvent A: 0.1% formic acid    -   Solvent B: 100% methanol

A sample of serum was diluted in solvent A. The column was equilibratedwith both multiport valves in the “LOAD” position (see FIG. 4A) using100% solvent A. 50 μL of the diluted sample was injected onto the columnusing 100% solvent A at a flow rate of 5 mL/min for 35 seconds. Thefirst multiport valve was switched to the “ELUTE” position (see FIG. 4B)and the column was backflushed with 100% solvent B at a flow rate of 1mL/min for 60 seconds to elute retained analytes from the column andinto the 200 μL sample loop. The first multiport valve was switched tothe “LOAD” position and the second multiport valve was switched to the“ELUTE” position (see FIG. 4C) and the eluted analytes were reapplied tothe column using 95% solvent A:5% solvent B at a flow rate of 1 mL/minfor 15 seconds. The analytes were eluted with a gradient of 95% solventA:5% solvent B to 100% solvent B at a flow rate of 1.6 mL/min over 200seconds and detected using the in-line mass spectrometer. A peakcorresponding to a retention time of 2.48 minutes was observed anddetermined to be estradiol. D8-estradiol was run as a separate samplefor use as an internal standard and exhibited a retention time of 2.48minutes. The resulting chromatograms are shown in FIG. 6.

To recharge the column for subsequent samples, the first multiport valvewas switched to the “ELUTE” and the second multiport valve switched tothe “LOAD” position and the column was backflushed with 100% solvent Bat a flow rate of 5 mL/min for 60 seconds. The first multiport valve wasswitched to the “LOAD” position and the column was equilibrated with100% solvent A at a flow rate of 5 mL/min for 40 seconds.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

The inventions illustratively described herein may suitably be practicedin the absence of any element or elements, limitation or limitations,not specifically disclosed herein. Thus, for example, the terms“comprising”, “including,” containing”, etc. shall be read expansivelyand without limitation. Additionally, the terms and expressions employedherein have been used as terms of description and not of limitation, andthere is no intention in the use of such terms and expressions ofexcluding any equivalents of the features shown and described orportions thereof, but it is recognized that various modifications arepossible within the scope of the invention claimed.

Thus, it should be understood that although the present invention hasbeen specifically disclosed by preferred embodiments and optionalfeatures, modification, improvement and variation of the inventionsembodied therein herein disclosed may be resorted to by those skilled inthe art, and that such modifications, improvements and variations areconsidered to be within the scope of this invention. The materials,methods, and examples provided here are representative of preferredembodiments, are exemplary, and are not intended as limitations on thescope of the invention.

The invention has been described broadly and generically herein. Each ofthe narrower species and subgeneric groupings falling within the genericdisclosure also form part of the invention. This includes the genericdescription of the invention with a proviso or negative limitationremoving any subject matter from the genus, regardless of whether or notthe excised material is specifically recited herein.

In addition, where features or aspects of the invention are described interms of Markush groups, those skilled in the art will recognize thatthe invention is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

All publications, patent applications, patents, and other referencesmentioned herein are expressly incorporated by reference in theirentirety, to the same extent as if each were incorporated by referenceindividually. In case of conflict, the present specification, includingdefinitions, will control.

Other embodiments are set forth within the following claims.

1. A chromatographic method for detecting one or more analytes in a bodyfluid sample containing a mixture of other substances, said methodcomprising: a) separating said one or more analytes from said other,substances in a mixture using a first chromatography column comprising amonolithic sorbent having macropores and mesopores, using a first mobilephase under conditions such that said one or more analytes are retainedon said first column and other substances are removed; wherein said oneor more analytes retained on said first column have a molecular weightof less than about 5,000 daltons, b) eluting said one or more retainedanalytes by applying a second mobile phase to the column, c) directingthe eluted one or more analytes to a second chromatography columnin-line with said first column for further separation, and d) detectingsaid one or more analytes following the separation in step c).
 2. Amethod according to claim 1, wherein said second mobile phase is appliedto the column in the opposite direction of the flow in step a).
 3. Amethod according to claim 1, wherein said body fluid is selected fromthe group consisting of blood, plasma, serum, bile, saliva, urine,tears, synovial fluid, peritoneal fluid, bronchial-alveolar lavage, CSF,and perspiration.
 4. A method according to claim 1 wherein saidmacropores have a median diameter of 0.1 to 50 μm.
 5. A method accordingto claim 4 wherein said macropores have a median diameter of 2 to 20 μm.6. A method according to claim 1 wherein said mesopores have a mediandiameter of 2 to 100 nm.
 7. A method according to claim 1, wherein saidmesopores comprise a fatty acid linked to said mesopore.
 8. A methodaccording to claim 7, wherein said fatty acid is selected from the groupconsisting of butyric acid (C4), caprylic acid (C8), and stearic acid(C18).
 9. A method according to claim 1, wherein said one or moreanalytes retained on said first column have a molecular weight of lessthan about 1,000 daltons.
 10. A method according to claim 1, whereinsaid one or more analytes retained on said first column have a molecularweight of less than about 500 daltons.
 11. A method according to claim1, wherein said other substances are proteins or proteinaceous material.